Using a Multimeter

Multimeter Functions
A useful debugging tool for any electronics technician is the multimeter. The multimeter allows us to measure continuity, resistance, and voltage.

Measure Continuity
The first exercise is to test the continuity of the PCB we just made to evaluate whether our soldering job was well or poorly done. We turn the dial on the multimeter until the the displays shows "OL" which stands for open loop. Then, we put each probe on a lead and a voltage reading should display, meaning our soldering job was successful.

Measure Resistance
The next exercise is to measure the resistance of some resistors and a potentiometer. We start by turning the dial of the multimeter to the resistance setting which should be marked by the Greek letter omega. 

Each of these resistors has a different resistance rating. We test each resistor and compare the values to the stated value determined by the colored stripes. We find very little discrepancy between the values (about 0.02%). We then measure the resistance of a potentiometer at varying resistance settings.

Potentiometer set to the lowest resistance.

Potentiometer set to the highest resistance.

Measure Voltage
Next, we measure the voltage of batteries. Before we begin, we turn the multimeter dial to measure the voltage of DC current. We put each probe on each of the electrodes of a 1.5 volt battery.

The multimeter displays 1.6 volts which is over the manufacturer's labeled voltage, meaning this battery probably has never been used. The next battery is a 9 volt battery.

The multimeter displays 3 volts which is below the manufacturer's labeled voltage, meaning this battery has little to no energy left for use. Our next task is to measure the voltage of a transformer and a switch-mode adapter. Our 9 volt transformer uses AC current so we must set the multimeter to read AC voltage.

We immediately notice that the voltage is exorbitantly higher than the manufacture's label. This is because transformers guarantee that the voltage supplied will be above the labeled voltage. Next, we add a resistor to see the effects on the voltage.

The voltage falls as expected. Next, we measure the voltage of a switch-mode adapter. We use the 5 volt power supply for our breadboard as a test case.

We measured about 4.8 volt which is normal for a switch-mode adapter since it is regulated.